This invention relates to a primary cell which contains thionyl chloride as at least part of the solvent for the electrolyte and/or as the positive active material. In particular, this invention relates to the deactivation of such cells.
Thionyl chloride cells have a number of advantages over other primary cell systems. The advantages include high energy density, flat discharge characteristics, excellent service over a wide temperature range, and good shelf life. These cells comprise an anodic material, usually lithium or calcium, a positive active material including thionyl chloride and aluminum chloride. Thionyl chloride cells can range in size from relatively small, e.g., "D"-cells, up to relatively large, e.g., about 1 ft.sup.3.
It is often desirable, or necessary, to deactivate primary thionyl chloride cells that may contain undischarged anode material, particularly damaged cells or damaged cells in which the anodes have become detached from their terminals. One prior art method for deactivating cells has been to discharge the cell, if possible, then open it and submerge it in water. Following deactivation the water is neutralized. Such a method has certain associated dangers. If the cell is not first discharged, it is inadvisable to submerge it in water. If a large quantity of anode material remains, the deactivation reaction can generate a great deal of heat. Regardless of the amount of anode material remaining, hydrogen gas is generated by the deactivation reaction. The deactivation reaction can form an insoluble product which plugs the spaces in the anode, thus preventing complete deactivation.
Another method for deactivating thionyl chloride cells comprised discharging the cell, if possible, opening the cell and flowing an aqueous gel into the cell. This method was largely unsuccessful.
Other methods for deactivating thionyl chloride cells have been proposed. Such methods generally have one or more drawbacks; they are dependent upon the condition of the cell, they introduce foreign material into the cell that may react in an unpredictable manner, or they produce products which restrict access to the anode and prevent complete reaction.
What is desired is a method for deactivating cells which employ thionyl chloride as the electrolyte solvent and/or cathodic reactant.
Accordingly, it is an object of the present invention to provide a method for deactivating thionyl chloride cells. Other objects and advantages of the present invention will become apparent to those skilled in the art from a reading of the following detailed disclosure and the appended claims.